Sheet metal work center and method therefor of fabricating worksheets

ABSTRACT

The invention relates to a sheet metal work center, in which a locking arrangement (15) is placed between the stationary part (9) of the buffer structure (2) and the releaser (13), wherein at least some of the vertical movements of the upper tool (7) and the releaser (13) can be implemented by using the transfer device (12), the stationary part (9) of the buffer structure (2) and the releaser (13) being connected with the locking arrangement (15).

FIELD OF INVENTION

The invention relates to a method for working with a sheet metal workcenter according to the preamble of claim 1.

BACKGROUND OF INVENTION

Generally in sheet metal working technology, for example in sheetpunching, certain components are always used. Such components includetools, punches, a releasing or stripper plate or a releaser, and acushion or stopper. In sheet punching, the machining is conducted in away that a punch is used to make a hole in a sheet against the cushion,and the punch is drawn out of the hole either by a spring force or byanother force, wherein the releasing plate prevents the punched sheet torise with the punch while maintaining the plate in its place. In sheetpunching, there are two possibilities to conduct the machining: first,the releasing plate remains in contact with the sheet to be punchedduring each punching stroke; or second, there is a certain air gapbetween the material to be punched and the releasing plate. Each methodhas its advantages, i.e., when there is a contact with the plate at thepunching stage, the plate will not vibrate during machining. On theother hand, when punching aluminium or materials which are soft or havea sensitive surface, the releasing force may become too great and leavescratches on the surface of the material. Because of this, it ispreferred that both alternatives be available in a sheet metal workcenter. Thus the releaser plate could be kept in place during thepunching strokes to achieve a permanent air gap, or the releaser platecould touch the material with every punching stroke.

Known sheet metal work centers use a single-tool system having a bufferor ram assembly, to which the drift or tool is mechanically fixed,wherein it can be exchanged, if necessary, either manually, by a robotor with a manipulator, and a releaser plate, wherein both are controlledwith a separate pressurized medium cylinder arrangement. This kind ofsolution involves, however, the problem that two separate shaft systemsare required for controlling the pressurized medium, and these must besynchronized with an NC control unit. This tends to delay the workingprocess. The single-tool system is relatively fast in the so-calledpassive mode, wherein the releaser, usually a releaser plate, isstationary at the distance of an air gap from the sheet to be workedduring the punching stroke. Thus the buffer, with the drift, can conductpunching strokes even at very short intervals. The problem is presentparticularly when the so-called active mode is used, wherein thereleaser plate is placed in contact with the surface of the sheet to beworked. Thus a need for so-called serial control arises, wherein theimplementation of the NC control unit requires first the informationthat the releaser plate is in contact with the surface of the sheet tobe worked before the buffer can be given a punching command. This factwill cause a delay of about one third in the working process when movingfrom the passive mode to the active mode.

SUMMARY OF INVENTION

With the present invention, it is possible to implement the workingprocess substantially at the same working speed irrespective of whetherthe active or passive mode is used, i.e., whether the releaser plate isat a distance of an air gap from the sheet to be worked or in contactwith said plate. Using the solution of the invention, theabove-mentioned working operations can be conducted with so-calledone-shaft control. The purpose of the invention is thus to raise thestandard of prior art and to present new surprising solutions for makingthe operations of sheet metal work centres more efficient and varied.

The invention is also related to a sheet metal work center.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail in the followingdescription with reference to the embodiment shown in the appendeddrawings, wherein:

FIG. 1 is a schematic general view of a sheet metal work centeraccording to the invention, shown in a vertical section,

FIG. 2 is a schematic illustration of the principle of the invention,shown in steps a to e, with the buffer structure according to the firstembodiment,

FIG. 3 illustrates the principle of the invention, shown in steps a tod, with the buffer structure according to the second embodiment,

FIG. 4 shows a vertical cross-section of the first embodiment of thebuffer structure with the locking arrangement released, and

FIG. 5 shows a vertical cross-section with the locking arrangementlocked.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, the reference numeral 1 indicates the machinebody of the sheet metal work center, having a buffer or punch structure2 placed in its upper part and a stopper structure 3 placed in its lowerpart. The machine body has either a closed, circumferential O-structureor an open structure having e.g. a C-, J-form or the like. FIG. 1 showsalso equipment related to the transfer device of the buffer indicatedwith the reference numeral 4, such as a hydraulic accumulator 4a and avalve block 4b. The sheet 5 to be worked is placed onto the machininglevel or worktable 6, underneath the upper tool or drift 7 and thereleaser or stripper plate 13 and above the lower tool die or stopper 8in the stopper structure 3 between releaser 13, upper tool 7 and lowertool 8. The sheet metal work center can be used for working at least thefollowing operations: punching, forming, screwing, and other generallyknown working operations to be conducted with a sheet metal work center.Normally, the upper tool 7 of the buffer structure 2 conducts the sheetpunching operations with a downwards directed working movement.Alternatively, the lower tool 8 can be used for forming, wherein theworking direction of the forming lower tool 8 is from below upwards. InFIG. 1, the reference numeral 15 indicates a locking arrangement forlocking the releaser 13, when necessary in situations to be described inmore detail below, to be stationary with the buffer fixing body 9.

FIG. 2 shows steps a to e illustrating schematically some work stages tobe conducted with the sheet metal work center. A punch stroke indicatesin this context the work cycle of the buffer 10 and the upper tool 7,including the working operation and the return movement to the startingposition.

FIG. 2a shows the buffer structure 2 and the stopper structure 3 in thetool exchange position, in which the upper tool 7 is exchanged in thebuffer structure 2. The buffer structure 2 comprises as main parts abuffer fixing body 9, at which the buffer structure 2 is fixed to themachine body 1. Further, the buffer or chamber structure 2 comprises thebuffer 10. Furthermore, the lower part of the buffer structure 2 isprovided with the upper tool 7 and the releasing plate or releaser 13surrounding the upper tool 7 and being connected with the releaser 13 bymeans of the transfer device 14 of the releaser 13.

A punching cylinder 12 used as the transfer device of the buffer 10 iseffective between the buffer 10 and the buffer fixing body 9, placed inthe upper part of the buffer 10.

FIG. 2b shows the punching cylinder 12 in the lowest possible position,that is, the punch stroke has been conducted without sheets 5. FIG. 2cshows a starting situation for a punch stroke, wherein the buffer 10 ismoved in connection with the sheet 5 in a way that the upper tool 7 andthe releaser 13 are at the distance of air gap 19 from the upper surfaceof the sheet 5. Thus the working levels of the upper tool 7 and thereleaser 13 are substantially at the same level. At this stage, thecontrol unit of the sheet metal work center can be used to selectbetween a so-called passive punch stroke, wherein the releaser 13remains at the distance of said air gap 19 (cf. FIG. 5) from the sheet5, retained in this position with a locking arrangement 15, and aso-called active punch stroke, wherein the releaser 13 is brought intocontact with the upper surface of the sheet 5. The operations related tothis selection will be described in more detail with particularreference to FIGS. 4 and 5.

FIG. 2d, in turn, shows the step of conducting an active punch stroke,wherein the locking arrangement 15 in connection with the buffer 10effective between the releaser 13 and the fixing body 9, is open (aswell as at the preceding steps 2a to 2c), wherein the combination of thebuffer 10 and the means 7, 13, 14 is moved downwards by the punchingcylinder 12 used as the transfer device of the buffer 10. When thereleaser 13 meets the surface of the sheet 5, the releaser transferdevices 14 yields in the longitudinal direction of the buffer 10,although generating a counterforce against sheet 5 at the end of thebuffer 10. One function of the transfer or cushion device 14 of thereleaser 13 is particularly to generate a controllable releasing force.FIG. 2d shows a situation in which the upper tool 7 has punched thesheet 5, penetrating underneath the upper surface of the lower tool 8 ofthe stopper structure 3 within the limits of the adjustable strokelength.

FIG. 2e shows the step of a passive punching stroke, wherein thereleaser 13 is locked to be stationary in relation to the buffer 10fixing body 9 by means of the locking arrangement 15, wherein thereleaser 13 is kept in place to maintain the distance of air gap 19 (cf.FIG. 5) to the sheet 5. The buffer 10, with the upper tool 7 fixed init, conducts a working movement downwards in relation to the bufferfixing body 9.

In an advantageous manner, the buffer structure 2 is substantially acylindrical form piece, wherein the buffer fixing body 9 comprises acentral hole, which holds the buffer 10 with a primarily rod-likestructure and the punching cylinder 12 used as the transfer device inthe upper part thereof. Parts 9, 10 and 15 comprise constructiveelements which can be used to constitute the embodiment of the bufferstructure 2 using pressurized medium, particularly hydraulic fluid.

FIG. 3 shows the operation of a second embodiment of the lockingarrangement of the invention in the buffer structure 2 of the sheetmetal work center. This buffer structure is illustrated in moretechnical detail with reference to the schematic view of FIG. 2, insteps a to d. FIG. 3a shows the position in which the upper tool 7 isabove the lower tool 8 and underneath the working level of the releaser13, the locking arrangement 15 being opened. FIG. 3b shows a situationwhich corresponds substantially to that shown in FIG. 2c, FIG. 3c showsa situation corresponding to that shown in FIG. 2d, and finally FIG. 3dshows a situation corresponding to that shown in FIG. 2e.

With particular reference to FIGS. 3a-d, the buffer 10 is furtherarranged to be rotatable around the central axis in the longitudinaldirection of the buffer structure by means of a rotating device 23arranged in connection with the buffer structure 2. Between the buffer10 and the buffer fixing body 9, a tooth wheel rim or a correspondingrotating means 23a is mounted on bearings 23c on the outer surface ofthe buffer 10 and driven by a worm pipe or a corresponding driving means30, which in turn is mounted on bearings on the buffer fixing body 9.This rotating device 23 is used to rotate the buffer 10 in relation tothe buffer structure 2 around the vertical axis to achieve the desiredangular position of the upper tool 7. Movements of the buffer 10 in thelongitudinal direction, such as the working movement, are achieved bypressurized medium supplied via a pressurized medium connector 28 intothe pressurized medium space 27 in the punching cylinder 12, wherein thebush-like rotating means, such as the tooth wheel rim 23a, surroundingthe outer surface of the buffer 10 is arranged in relation to the fixingbody 9 of the buffer 10 in a way that the necessary relative movement inthe longitudinal direction of the buffer 10 takes place between theinner surface of the rotating means, such as the tooth wheel rim 23a,and the outer surface of the upper part of the buffer 10 during workingand return movements of the buffer 10 (surface 31). For transmission ofthe rotating force, a wedge part 23b is provided between the parts 10and 23a.

In the lower part of the buffer structure 2, in turn, the transferdevice 14 of the releaser 13 is arranged. It consists of a recess in theinner surface of the buffer fixing body 9 in the longitudinal directionof the buffer structure 2 and a collar structure in the lower part ofthe buffer 10, thus forming a pressurized medium space 34. In acorresponding manner, the bush-like fixing part 13a of the releaser 13is provided with a radial annular front surface 35 facing thepressurized medium space 34. The front surface 35 is movable in thelongitudinal direction of the buffer structure 2 in the recess 32 in thebuffer 10. With the pressurized medium space 34, a connection 36 forapplying through pressurized medium holes or the like to the pressurizedmedium space 34 are provided, for achieving the different positions.

The upper part of the buffer fixing body 9 is provided with the punchingcylinder 12 of the buffer 10, placed in the pressurized medium space 27in the fixing body. A pressurized medium channel 28 is connected to thepressurized medium space 27.

The lower part of the buffer 10 is provided with an exchange arrangementfor the upper tool 7. In connection with the tool exchange arrangement,there is a locking mechanism comprising the combination of a lower chuck49, a rod 50 and a piston part 51. This combination is placed incorresponding cylindrical holes in the buffer 10 in the longitudinaldirection. The upper part of the locking mechanism is placed inpressurized medium space 52, wherein the lower surface of the pistonpart 51 is acted against by the pressurized medium at a pressureeffective through pressurized medium connector 53a, which extendsthrough the fixing body 9. The locking mechanism is shown to move to itsupper position in FIGS. 3b-d. In a corresponding manner, for an effecton the upper surface of the piston part 51 through pressurized mediumconnector 53b, placed in the fixing body 9 and penetrating the same, thelocking mechanism moves to its lower position in the longitudinaldirection of the buffer 10, wherein the upper tool 7 can be exchanged(FIG. 3a). In connection with the upper tool 7, there is a fixing means54 for fixing the upper tool into the lower chuck 49, at its counterpart55.

FIG. 3 shows a first embodiment of the locking arrangement 15. Thus thebuffer fixing body 9 is provided with a guide 60, the body 61 of thefixing arrangement 15 being arranged to be moved and locked in relationto this guide 60 in the longitudinal direction of the buffer structure2. In their cross-section, the guide 60 and body 61 form a T-joint. Withthe body 61, there is a lockpin cam 63 or the like articulated to berotatable in the vertical direction in relation to the horizontal joint62. At the tip of the lockpin cam 63, on its horizontal front surface64, there is a groove or notch 65 which in the so-called passive mode isplaced in connection with the ring flange 66 surrounding the outersurface of the fixing part 13a of the releaser 13, when the releaser 13is driven with the buffer structure 10 to the distance of the air gap 19(FIG. 5) from the lower tool. In the shown embodiment, the groove ornotch 65, with its radial front surfaces, is placed against the radialfront surfaces of said ring flange 66, on their both sides, to surroundthe flange 66. Furthermore, the radial surface 67 adjoining the upperedge of the front surface 64 of the lockpin cam 63 is placed against thelower front surface 9a of the buffer fixing body 9. In this way thereleaser 13 can be coupled with the machine body 1 as a substantiallysolid piece to receive possible loads in the longitudinal direction ofthe buffer 10. Thus the locking part 15a of the locking arrangement 15,seen in its vertical cross-section, has the primary shape of an L-formedpiece whose vertical upper part 15p comprises said joint 62 fixed to it,and whose horizontal lower part 15v comprises said other partsfunctional in locking. In a horizontal cross-section, the locking part15a forms a curve which is placed on the outer ring of the ring flange66, on part of its circumference.

Further with reference to FIGS. 4 and 5, a unit comprising substantiallythe corresponding elements in a different construction is presented inthis embodiment. Consequently, the corresponding parts are indicatedusing the reference numerals of FIG. 3. The locking arrangement 15 andthe lockpin cam 63 belonging to its locking part 15a are rotated byusing an actuator, such as a cylinder-piston mechanism 68, placed in thebody 61 and using a pressurized medium, and being connected with therotatable pin 69 in the locking part 15a. Further, the body 61 isprovided with a body 60 transfer device 70 for movements in relation tothe fixing body of the buffer 9. This transfer device 70, which is anactuator using e.g. pressurized medium, such as a cylinder-pistonmechanism, is effective between the buffer transfer body 9 and the body61. In a corresponding manner, the releaser 13 body 13a is in thisembodiment provided with a groove 65, in which the tip 66 of the lockpincam 63 or the like is inserted.

The hydraulic control of the sheet metal work center presented above canbe implemented with normal hydraulic components and control mechanismsbetween them which are known in a way obvious to an expert in the art sothat they will not be discussed in this context.

We claim:
 1. A method of operating a sheet metal work center having a body, a work table whereon a sheet to be worked is placed, upper and lower tools in punch and stopper structures, respectively, for effecting work on said sheet on its opposite sides, a releaser in operative connection with said upper tool, and a transfer device for moving said upper tool and said releaser in the vertical direction, comprising the steps of:a) placing a locking arrangement between a stationary part of said punch structure and said releaser; and b) utilizing said transfer device to drive said upper tool and said releaser to move relative to said lower tool (1) in a passive mode with said locking arrangement locked wherein said releaser is at a given distance from the surface of said sheet, or (2) in an active mode with said locking arrangement opened wherein said releaser is in contact with the surface of said sheet.
 2. Sheet metal work center comprising:a body; a work table whereon a sheet to be worked is placed; upper and lower tools in punch and stopper structures, respectively, for effecting work on said sheet on its opposite sides; a releaser working in cooperation with said upper tool; a transfer device for moving said upper tool and said releaser in the vertical direction; and a locking arrangement placed between a stationary part of said punch structure and said releaser, wherein said upper tool and said releaser are adaptable to be driven by said transfer device to move along said vertical direction, said stationary part of said punch structure and said releaser being connected with said locking arrangement.
 3. Sheet metal work center according to claim 2, wherein said upper tool and said releaser are placed in said punch structure, said punch structure including a punch fixing body, said punch structure being mounted in said body of said sheet metal work center.
 4. Sheet metal work center according to claim 3, wherein said punch structure includes a chamber; andwherein said locking arrangement is operational between the outer surface of said punch fixing body and a releaser fixing part associated with said releaser on the outer surface of said chamber.
 5. Sheet metal work center according to claim 3, wherein said locking arrangement is arranged in the locking position to be supported against the lower front surface of said buffer fixing body.
 6. Sheet metal work center according to claim 2, wherein said punch structure includes a chamber, said work center further comprising:a cushion device placed between said punch and said releaser for moving said releaser in the longitudinal direction of said punch structure in relation to said chamber.
 7. Sheet metal work center according to claim 2, wherein said locking arrangement comprises a guide placed in a punch fixing body of said punch structure; andwherein said locking arrangement comprises a body arranged to be moved and locked in relation to said guide in the longitudinal direction of said punch structure.
 8. Sheet metal work center according to claim 2, wherein said locking arrangement comprises a locking part movably coupled to a horizontal joint in a body of said locking arrangement, said locking part being pivotable between the open and locked position of said locking arrangement.
 9. Sheet metal work center according to claim 8, wherein said releaser comprises a releaser fixing part; andwherein said locking part of said locking arrangement, in its substantially vertical cross-section, is L-shaped, said locking part having a horizontal lower part that is matable with a counterpart of said releaser fixing part.
 10. Sheet metal work center according to claim 8, wherein said releaser comprises a releaser fixing part; andwherein the locking of said locking arrangement is effected as a groove-cam locking between said locking part and said releaser fixing part.
 11. Sheet metal work center comprising:a body; a work table whereon a sheet to be worked is placed; upper and lower tools in punch and stopper structures, respectively, for effecting work on said sheet on its opposite sides; a releaser working in cooperation with said upper tool; a transfer device for moving said upper tool and said releaser in the vertical direction; and a locking arrangement working cooperatively with said releaser, and adaptable to lock said releaser in a position fixedly spaced from the top surface of said sheet as said upper tool is driven by said transfer device to effect work on said sheet.
 12. Sheet metal work center of claim 11, wherein said locking arrangement is further adaptable to not lock said releaser in place while said upper tool is driven by said transfer device so that as said upper tool is effecting work on said sheet, said releaser is in contact with the top surface of said sheet.
 13. Sheet metal work center of claim 12, wherein said locking arrangement is engaged to said releaser to lock said releaser in place when said work center is in an active mode, and is disengaged from said releaser when said work center is in a passive mode.
 14. A method of effecting work in a sheet metal work center having a body, a work table whereon a sheet to be worked is placed, upper and lower tools in punch and stopper structures, respectively, for effecting work on said sheet on its opposite sides, a releaser working in cooperation with said upper tool, and a transfer device for moving said upper tool and said releaser in the vertical direction, comprising the steps of:a) effecting a locking arrangement to work cooperatively with said releaser; and b) actuating said locking arrangement to (1) lock said releaser in a position fixedly spaced from the top surface of said sheet as said upper tool is driven by said transfer device to effect work on said sheet, or (2) not lock said releaser while said upper tool is driven by said transfer device so that as said upper tool is effecting work on said sheet, said releaser is in contact with the top surface of said sheet. 